STOCK PURCHASE AGREEMENT

This Amendment No. 3 (this “ Amendment ”), dated December 18, 2008, to the Stock Purchase Agreement (as defined below) is made by and among Vector Intersect Security Acquisition Corporation, a Delaware corporation (“ Parent ”), Cyalume Acquisition Corp., a Delaware corporation (“ Purchaser ”),   Cyalume Technologies, Inc., a Delaware corporation (the “ Company ”), and GMS Acquisition Partners Holdings, LLC (“ Seller ”).  Any capitalized term not defined herein shall have the meaning for such term specified in the Stock Purchase Agreement.

WHEREAS , Parent, Purchaser, the Company and Seller entered into a Stock Purchase Agreement dated February 14, 2008, Amendment No. 1 to the Stock Purchase Agreement on October 22, 2008, and Amendment No. 2 to the Stock Purchase Agreement on December 17, 2008 (as amended, the “ Stock Purchase Agreement ”);

NOW THEREFORE, in consideration of the foregoing and the representations, warranties, covenants and agreements herein contained and other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the parties hereto hereby agree as follows:

1.   The text of Section 2.4(e) of the Stock Purchase Agreement is hereby deleted in its entirety and replaced with the following:

“Adjustment to Estimated Purchase Price.

(i)           If the Actual Adjustment is a positive amount, Parent shall promptly pay the amount of the Actual Adjustment by issuing shares of Parent Common Stock, with an aggregate value (based on the Average Trading Price as of the date of determination of the Actual Adjustment) equal to the Actual Adjustment plus 12,314 shares of Parent Common Stock, to those Members who held Common Units as of the Closing Date (on a pro rata basis based on the number of Common Units held by each Member as of immediately prior to the Closing), as set forth in a written notice by Seller or Cova.

(ii)           If the Actual Adjustment is a negative amount, then Seller or Cova shall promptly pay Parent the amount of the Actual Adjustment by instructing the Escrow Agent to deliver to Parent such number of shares of Escrowed Stock that has an aggregate value (based on the Average Trading Price as of the date of determination of the Actual Adjustment) equal to the Actual Adjustment (the “ Negative Adjustment Shares ”) less 12,314 shares of Parent Common Stock; provided , that if the number of shares of Parent Common Stock payable to Parent under this Section 2.4(e)(ii) is le